Profile Subject 2 (second elective discipline)
Profile Subject 2 is the second elective paper; its score is added to Profile Subject 1, and thresholds are set on the sum of the two. A strong first paper cannot carry a weak second, so plan the pair as one block of work on a shared revision schedule instead of treating the second subject as spare.
Where the marks are
- The two papers share a method: read the quantity asked for, convert inputs to a common unit, apply the rule, convert back
- Multi-step problems are usually two school rules chained, not a new rule
- Formula sheets, where provided, save memory but not method - you still choose the formula
- Data-based items reward checking units and significant figures
Worked example (Chemistry - swap in your own subject)
4.0 g of NaOH is exactly neutralised by 0.50 M HCl. What volume of acid is needed? (Mr NaOH = 40) n(NaOH) = 4.0 / 40 = 0.10 mol. NaOH + HCl → NaCl + H₂O, ratio 1:1, so n(HCl) = 0.10 mol. V = n / c = 0.10 / 0.50 = 0.20 L = 200 cm³. The chain is: mass → moles → equation ratio → moles → volume. Every link is checkable on its own.
Traps
- Using mass where moles are required
- Ignoring coefficients in the balanced equation
- Mixing cm³ and dm³ (1 dm³ = 1,000 cm³)
- Overlooking purity or percentage yield when the question supplies them
- Rounding molar masses to whole numbers when the data gives 40.0 and 58.5